Air screw



May 23, 1933. c. E. McGulRE AIR SCREW Filed Feb. e. 1952 /m/en for Patented' May 23, 1933 cuor; E. macina, or DOUGLAS, ARIZONA AIR SCREW Application -led February 9, 1932. Serial No. 591,787.

This invention relates to an improvement on an air screw for an aircraft of the helicopter type and is an improvement on the lifting described in my patent specification,

seria1N0.490,242,1ed October 21, 1930.

The object of this improvement is to provide an air screw prove its aerodynamic A further Iobject is lo pitch air screw of high not incur structural diiii of high aspect ratio to imefliciency. v j

to provide a variable aspect ratio which will culties.

A still further object 1s to provide a variaable pitch air screw of which aspect ratio which will have sufiicient structural strength,

.15 and win Sau be iight enough in weight to make -it satisfactory for aeronautical" purposes.

A still further object is to provide an screw which will operatein varying wind' air conditions without chatter or vibration.

In my previous use a relatively short design it was necessary to and thick airfoil on my screws to enable me to inclose a tubular beam 'I within the airfoil of sufcient strengthl -to withstand the external forces `on the airfoil.

This arrangement proved ineicient and otherwise unsatisfactory,

as.' all the flutter and vibration of the screws in a rigid conofthe aircraft.

struction would be transmitted into the body The only features of my previous patent which I have incorporated in this improvement is the flexible steel cable connectmg the` airfoils to balance their centwo opposing trifugal force, and the the airfoils around the trol their pitch is similar.

to perform in this dehas another function method of swiveling tubular beamA to con- Thesteel cable `sign however, in addition to supporting the centrifugal force of the airfoils it must bend Vas the airfoils deflect from a line normal to their supporting` beam, at a positive pitch, or force, cause them to deect up force is balanced since the steel cable is when the screw is set to produce a'lifting the wind pressure on the airfoils will ward until the lifting by the centrifugal force, and

acting in a direction normal to the resultant of these two forces, it is in reality supporting the liftingforce of the screws as well as th eir centrifugal force;

wardso that there is very little load on the universal joints, and their principal function is to hold the airfoils in their proper position with relation to their supporting beam and to provide a flexible connection to the controls so that the pitch of the airfoils may be varied'while they are at the same time free to defiect in any direction.

lWith the above and other objects invview.

the invention consists in certain novel details l of construction and combination of parts `hereinafter fully described and claimed, it being understood that various modifications may be resorted to within the scope of the apelevation of the center portion of the screw,

showing the flexible steel cable for supporting the centrifugal force of the airfoils, aswell as the external forces on them ,the universal joint positions the inner en-d of the airfoils and forms a connectionto the pitch controls,and a cantilevered sprin which supports the-dead weightof the air oil when it is at rest, and vthe dotted lines indicate the angular position the airfoils may take to assume a neutral position between the wind forces on them and their centrifugal force. Fig. 3 is a cross section of the -airfoil at the universal joint which positions the inner end ofthe airfoil.

Fig..4 is an end view of the screw showing in dotted lines the method of altering the pitch of the screws.

Referring now lto thcl drawing in which like characters of reference designate similar parts in the various views, 5 designates the screw blades or airfoils, which are mounted on a short tubular beam 6 through universal joint 7 land sleeve 8, Fig.,2; sleeve-8 rotates WJ titi about beam 6 rotating airtoil 5 to alter its pitch and twisting flexible steel cable 9; sleeve 8 and airfoil 5 are flexibly connected by universal joint 7; to airfoil 5 is attached rib l0, to which cable 9 is attached by pin 1l which passes through a loop in the end of cable 9. Attached to sleeve 8 is a cantilevered spring 12 which will support the Weight of the airtoils when the screw is at rest or turning too slow for their centrifugal force to vsupport their weight, to prevent them from drooping down and striking obstructions, but which will deflect in any direction with very little strain on the airfoils and allow them to assume a neutral position between the external forces on the airtoil and their centrifugal torce to eliminate any appreciable bending moment on the airfoils. Airteils 5 will be a recognized airioil as to camber,.and can be made very .light in construction, needing very little internal bracing due to the absence ot bending moments in their structure.

To sleeve 8 is also attached lever 13 which in turn is connected to sliding yoke 14; in lliig.` a by connecting rods l5; yoke la will slide up or down on axle 16 to alter the pitch of the screw as shown in dotted lines in Fig. t; yoke lt will be operated by a control arrangelment similar to that which wasused in my previous patent application, Serial No. 4:90, 242, and' oct. ai, i930.

From the above. description it is thought that the construction and operation of the invention will beclearly understood without further explanation.

Having thus described the invention, lt claim: H

Il. lin an aircraft, an air screw including a short tubular beam, airfoils swiveled on the ends of the beam through a universal joint, a steel vcable passing through the beam and connected to said airtoils for equalizing the thrust as well as resisting the external forces on the airioils, and means.. Jfor varying the pitch of said airfoils on the beam.

2. lin an aircraft, an air screw com rising a. short tubular beam, an axle secur to the beam for revolving the beam, opposing airfoils flexibly connected to a rotatable sleeve on thefends of the beam, a cable passing through the beam and connecting said airfoils together, and a sliding yoke on said axle operatively connected to a lever on the rotatable sleevev for changing the pitch angle of said airfoils. i f

3. lln an aircraft, an air screw includingfa short tubular beam, opposing airfoils 'Hexibly connected to rotatable sleeves on the end of said beam, cantilevered springs attached to the said sleeves and supporting the dead weight of said airioils when said a-ir'foils are at rest and to prevent them from drooping down and striking obstructions, an axle se` cured to substantially the center point of the short tubular beam, airfoils flexibly conf nected to swivel mountings on the ends of said beam at substantially the center of pressure of said airfoils, and a cable housed within the airfoils and said beam, and securely attached at the ends to the airfoils for equalizing the centrifugal thrust of, and resisting the external forces on said airioils.

5. ln an aircraft7 an. airscrew comprising a short tubular beam, a steel cable passing through said beam, airi'oils of substantially identical structure as to size camber and construction, iexibly connected to a swivel mounting on the ends of said beam, a rib secured within the airfoils provided with suitable means of connecting said rib to said cable for transmitting the combined centrifugal thrust and lifting force of the airfoils to the cable to equalize the forces oi the opposing airfoils.

6. ln an aircraft, an air screw comprising a tubularbeam, an axle attached to said beam for rotating said beam, rotatable sleeves on the ends oi said beaml with universal joints around their outer ends, airfoils with their inner ends attached to said universal joints so that said airfoils may deflect about this joint to assume a neutral position between the centrifugal forcefof and the external forces,

on said airfoils to eliminate bending stresses in said airfoils, a cable passing through saidl beam and terminally connected tousaid airtoils for equalizing' the forces imposed by the opposing airoils, means of supporting said airfoils when screw is at rest.

' C. E. MCGUIRE.

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